What is the best way to insure that you edges are square to the cutter?

Normally we cut pieces out of a sheet of material. The material is larger than the piece you are going to cut. If you are cutting cabinet parts you have waste and so it doesn't matter if your sheet is square.

I have been approached by a new client, I hope, that needs designes cut into the full sheet of material. He sent me some examples of the designs he needs cut and they are mostly rectangle that have to square to the top, bottom and sides.

A snag is that the raw boards from the board supplier are often not square to start with. We only line up one long edge of the board parallel to the x-axis.

For a reference edge, to bump the board up against, there are a couple of experiences learnt:
- long edges are not needed, two short blocks of scrap are enough. (easier to clean out the sawdust between cuts)
- A rebate under the edge is useful for the trapped sawdust (elevates the reference above the table)
- We clamp the reference blocks to the cross-supports, about 20mm away from the table edge, and drop in spacers when setting up. This gives the cutter room to trim around the board without hitting the references.
- The outer edges of the boards are always trimmed by a mm or three

The customer is made very aware of the squareness, edge conditions and likely sizes of boards from various suppliers